CN112689701B

CN112689701B - Turbine engine inner casing with improved insulation properties

Info

Publication number: CN112689701B
Application number: CN201980059520.0A
Authority: CN
Inventors: 克里斯托夫·斯科尔特斯
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2018-09-24
Filing date: 2019-09-17
Publication date: 2024-03-15
Anticipated expiration: 2039-09-17
Also published as: FR3086323B1; US11566538B2; CN112689701A; FR3086323A1; EP3833854A1; WO2020065178A1; CA3111075A1; US20220034236A1

Abstract

The invention relates to an inner housing collar (50) for a turbine engine centered on a longitudinal central axis, comprising: a body (51) centred on said axis, both ends of which are delimited by surfaces radially internal and external with respect to said axis; a porous structural insulating sleeve (52) having a volumetric porosity of greater than or equal to 50%, comprising: lateral portions completely covering both ends; the outer portion (52 a) and the inner portion (52 b) completely cover the radially outer and inner surfaces, respectively, of the body when viewed in a section transverse to said axis; and a protective sleeve (53) which at least partially covers the insulating sleeve (52) and which comprises a radially outer protective portion (53 a) and an inner protective portion (53 b) which at least partially cover the outer portion (52 a) and the inner portion (52 b), respectively, when viewed in a section transverse to said axis.

Description

Turbine engine inner casing with improved insulation properties

Description

Technical Field

The present invention relates to the insulation of turbine engine inner casings, in particular of aircraft turbine engines.

Background

The compressor and turbine of a turbine engine typically include at least one rotating assembly or rotor, which typically includes a plurality of disks. Each rotor disk is provided with a plurality of rotor blades and rotates relative to a stationary collar circumferentially surrounding each disk. The set of ferrules facing the blades constitutes the inner casing of the turbine engine.

Stator blades (also known as "rectifiers" for compressors, and "distributors" for turbines) may be interposed between the two rotor disks and form a stator integral with the inner casing.

It is necessary to maintain a gap between the blade tips of the rotor disk and the collar of the inner casing. Ideally, such clearances should be minimized to improve turbine engine performance. However, these clearances must be accounted for during turbine engine operation.

These clearance variations are mainly mechanical phenomena (especially due to deformation of the rotor under centrifugal force, the influence of the pressure of the gas channels on the rotor and stator, axial displacements, etc.) and thermal phenomena (in compressors, especially in high-pressure compressors, the parts forming the rotor and stator usually have different coefficients of thermal expansion, especially with different deformation speeds due to different circumstances; in general, the stator has a greater ventilation, a smaller mass, a reaction speed faster than the rotor disc, while the inertia of the rotor disc is mainly related to the mass of the disc root, usually the ventilation is small, this difference in "thermal response time" will lead to a significant variation in the clearance during operation.)

Reducing running clearances is an important approach to improving turbine engine performance.

The solutions proposed in the prior art generally require techniques capable of reducing the "thermal response time" of the inner shell. In most cases, the proposed solution consists in providing the inner wall of the inner shell with annular members arranged in line with the stator to form one or more air gaps, thereby providing the inner shell with thermal insulation. It is recalled that the air gap is a closed, narrow annular space in which there is air. This solution is described for example in document [1] and shown in fig. 3 and 4, which will be described in detail below.

However, the air gap solution as a means of insulation requires the use of many parts (the latter annular part and fastening part), which can affect quality and cost. There are also installation limitations and space issues.

Furthermore, it is necessary to insulate the air gap well by using sealing means such as rings, sealing sheets, etc., since the deterioration of the seal actually means a deterioration of the gap.

Furthermore, the air gap solution may make it possible to insulate the inner wall of the inner shell locally in line with the stator, but not completely insulate the skin of the inner shell. In particular, depending on the chosen configuration, it is possible that there is no insulation towards the inner wall of the rotor; the side wall of the inner shell corresponding to the pipeline sampling opening is not insulated; the outer wall of the inner shell is not insulated.

Finally, due to lack of space or difficulty in access, it is sometimes not possible to build such insulation systems through an air gap in existing turbine engines.

Accordingly, there is a need to optimize the insulation of the turbine engine inner casing skin.

Disclosure of Invention

To meet this need, the object of the present invention is to provide an inner casing collar for a turbine engine, said collar being centred on a longitudinal central axis, characterized by comprising:

-a body centred on a longitudinal central axis, said body comprising two longitudinal ends and being delimited by a radially inner surface and a radially outer surface with respect to the longitudinal central axis;

-an insulating sleeve comprising:

lateral covering portions completely covering the two longitudinal ends of the body;

an outer covering portion completely covering the radially outer surface of the body along a section transverse to the longitudinal central axis;

an inner covering portion completely covering the radially inner surface of the body along a section transverse to the longitudinal central axis;

a lateral portion connecting the inner and outer portions; and

-a protective jacket at least partially covering the insulating jacket and comprising, along a section transversal to the longitudinal central axis:

a radially outer protection portion at least partially covering the outer covering portion; and

a radially inner protection portion at least partially covering the inner covering portion;

and wherein the sleeve has a porous structure with a volumetric porosity of greater than or equal to 50%.

Preferably, the ferrule is a unitary component.

According to the invention, the insulating sleeve having a porous structure completely covers the main body to insulate it, and the protective sleeve at least partially covers the insulating sleeve. In practice, the protective sleeve covers the sleeve at least over the portion of the sleeve that will be in contact with the fluid flow of the turbine engine.

In the context of the present invention, the proportion of empty spaces (voids, i.e. interstitial voids that are connected together or not) contained in the considered region is expressed in terms of volume porosity. Thus, the volumetric porosity of a region (e.g., a sleeve) is the ratio between the pore volume of the region and the total volume of the region (structure + pore, i.e., solid structure). This may be open and/or closed pores.

There are a number of methods for analyzing porosity. The most common are microtomography, ultrasound and image analysis.

Microtomography is a non-destructive three-dimensional analysis technique that can provide volumetric images of the linear absorption coefficient distribution of X-rays. A 3D map of the porosity in the material can be obtained and then the volume percent of the interstices calculated.

Ultrasound is a non-destructive testing technique that can estimate porosity in the event that the porosity strongly interferes with ultrasound propagation by comparing the amplitude differences between the input signal and the output signal.

Image analysis includes enumerating porosity on an image obtained, for example, using an optical microscope or a scanning electron microscope.

In the context of the present invention, this requires a porous structure, i.e. a structure formed by a solid material and one or more cavities (typically filled with air) located inside the solid material. An example of a porous structure is shown in fig. 7: there is a volume of solid material 54 in which the cavity 55 is dispersed. The cavity has a minimum volume that will allow the porous structure to have as high an air density as possible and at least greater than 50% to provide good thermal insulation of the body.

According to a first alternative, the main body and the outer and inner cover portions each extend over 360 ° around the longitudinal central axis 24. There is thus an annular collar as shown in fig. 5.

According to a second alternative, the main body and the outer and inner cover portions each extend over the same angular sector of less than 360 ° around the longitudinal central axis. Thus, there is a ferrule with an angular section, as shown in fig. 6. Advantageously, according to this second alternative, the body has two opposite circumferential ends, and the sleeve further comprises an intermediate covering portion connecting the outer and inner covering portions and completely covering each opposite circumferential end of the body. Preferably, the protective sleeve further comprises an intermediate protective portion connecting the radially outer protective portion and the inner protective portion and entirely covering the intermediate covering portion.

According to an alternative, the radially outer and inner protective portions of the protective sleeve completely cover the outer and inner cover portions of the insulating sleeve, respectively. Preferably, the protective sleeve completely covers the insulating sleeve.

Preferably, the protective sheath has a volume porosity of less than 5%. Thus, the protective sleeve has a dense structure with little voids. The presence of this protective sleeve in the collar makes it possible to maintain an acceptable surface condition of the engine in terms of roughness, thus preventing excessive load losses in the duct and non-duct air circuits.

Advantageously, the insulating sleeve has a microporous structure, preferably a cellular microporous structure or a lattice structure.

The microporous structure comprises a plurality of cavities (cells) delimited by walls. The cells may have various shapes, such as hexagonal, cubic, etc.

The lattice structure is a three-dimensional structure comprising a single cavity, the walls of which are connected by a frame (e.g., struts) having a lattice shape.

In one case, the porosity of the microporous and lattice structures is primarily due to the cells, and in another case, to the individual cavities. The walls of the microporous and lattice structures may also be porous (e.g., made by powder sintering); preferably, these walls are dense with a volume porosity of less than 5% to ensure a porous structure with sufficient mechanical resistance.

According to one embodiment, the body, sleeve and sleeve are made in one piece by additive manufacturing to form a monolithic and integral component.

According to one embodiment, the ferrule comprises a strip of abradable material integrated into the ferrule by being manufactured directly in the protective sleeve.

It is also an object of the present invention to provide a turbine engine inner casing comprising at least two ferrules as described above arranged axially adjacent to each other. Preferably, at least one collar of the inner shell is used to support the stationary blades.

Finally, it is an object of the present invention to provide a turbine engine equipped with such an inner casing.

According to one embodiment, a turbine engine includes moving blades, and at least one ferrule includes a strip of abradable material added to the at least one ferrule in line with the moving blades.

The present invention has a number of advantages.

The solution proposed by the invention makes it possible to completely insulate the skin of the inner shell on all its faces and is simple to implement, both in the case of installing a collar with angular segments to form an annular collar, and in the case of installing a plurality of longitudinally adjacent collars to form the inner shell, on the one hand, and in the case of manufacturing the collars, on the other hand.

In particular, the insulation of the inner shell is optimized with respect to the prior art, its skin (i.e. its inner wall, its outer wall and its side walls (corresponding to the sampling area of the air flow)) being insulated. In particular, while prior art solutions with air gaps in configurations where the air gap is only arranged in line with the stator (and not with the rotor) do not allow to insulate the area between the two air gaps, the area where the heat flow flows through by conduction, the solutions proposed in the context of the present invention make such insulation possible.

Furthermore, while in the case of the air gap insulation system according to the prior art leakage at the interface between the elements constituting the air gap (e.g. the interface of the stator and the inner wall of the housing) would generate an air flow having a high adverse effect on the gap variation, the effect of such leakage of the inner housing according to the invention no longer interferes with the gap. In fact, the adverse effect of these leaks is to increase the response time of the inner shell, which is no longer present since the insulating sleeve is porous, the effect being that the core (i.e. the body) of the inner shell is completely insulated from the outside; in other words, the skin of the inner shell is completely insulated.

Finally, the inner casing obtains a better insulation effect, thereby reducing the clearances during operation and thus reducing the unit consumption of the turbine engine. The performance of the turbine engine and its operability are thus improved.

Furthermore, the size of the insulation layer of the inner casing may be smaller than the size created by the air gap solution (e.g., in a configuration where the rectifier is integral with the inner skin of the casing (fig. 4)), which makes it easier to install on the turbine engine.

Drawings

Other aspects, objects, advantages and features of the invention will appear better upon reading the following detailed description of a preferred embodiment, given as a non-limiting example and with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic view of an axial cross-section of an aircraft turbine engine;

FIG. 2 is an enlarged view of the high pressure compressor of FIG. 1;

FIGS. 3 and 4 are enlarged views of an upstream portion (FIG. 3) and a downstream portion (FIG. 4), respectively, of the stator of the compressor of FIG. 2, with the inner casing thereof insulated by an air gap, according to the prior art;

FIG. 5 is a schematic cross-sectional view of an embodiment of a ferrule according to the present invention;

FIG. 6 is a schematic cross-sectional view of another embodiment of a ferrule according to the present invention;

FIG. 7 shows an example of a porous structure for a sleeve in cross-section;

FIGS. 8a and 8b show examples of lattice structures;

FIG. 9 shows an example of a microporous structure;

FIG. 10a is a view of an upstream portion of a compressor stator having an insulated inner shell according to the present invention;

FIG. 10b is an exploded view of the various components of FIG. 10 a;

FIG. 11a is a view of a downstream portion of a compressor stator having an insulated inner shell according to the present invention;

fig. 11b is an exploded view of the various components of fig. 11 a.

Detailed Description

Referring first to fig. 1, a turbine engine 1 of an aircraft of the bypass turbine engine type is shown. The turbine engine 1 comprises, from upstream to downstream in the main flow direction of the gas indicated by arrow 11, a low pressure compressor 12, a high pressure compressor 14, a combustion chamber 16, a high pressure turbine 18 and a low pressure turbine 20, these elements defining a main duct 21 through which a main gas flow 22 passes. The fan 28 is rectified by the nacelle 30 to produce a secondary flow 32 through the secondary duct 31.

Fig. 2 is a general view of the high pressure compressor 14 of fig. 1. The compressor 14 comprises a central rotor 26 driven by a series of shafts 2 and consisting of a set of streamlined models (shapes) 3 consisting of rings 4 juxtaposed and separated by a plurality of discs 5 in line with a plurality of moving blades 6. The stator 7 encloses the rotor 26 and comprises an outer shell 8 and an inner shell 10, the inner shell 10 being formed by axially juxtaposed annular collars 40, turning the rotor 1. The inner casing 10 serves to define an annular duct 15 for the flow of the main air flow 22 therein, in which a plurality of moving blade 6 stages extend, in which a plurality of stator blade 13 stages for guiding the air flow extend, which stator blade stages are connected to an annular collar 40 and alternate with the moving blade stages described above.

Fig. 3 and 4 are enlarged views of an upstream portion (fig. 3) and a downstream portion (fig. 4) of the stator of the compressor shown in fig. 2, respectively, which illustrate solutions for insulating the inner wall of the inner casing 10 by an air gap according to the prior art.

In fig. 3, the inner shell 10 consists of annular collars 40 which are connected together by bolts 42 clamping flanges 41, the bolts terminating in the flanges. These annular ferrules 40 include radially inward projections 43 which open into the duct 15 for air flow and are therefore exposed to their temperature.

The support ring 44 of the stator vane 13 makes it possible to attach the stator vane 13 to the annular collar 40 and form an air gap 45. A layer of abradable material 46 is disposed on the collar 40 in line with the rotor 6.

In fig. 4, the inner housing 10 comprises an annular collar 40, the annular collar 40 being connected in particular by a separate seal 37 having a U-shaped portion. The elements 8',47 are connected to the annular collar 40 to form an air gap 45.

It can be observed that these solutions of the prior art do not allow optimal insulation of the inner shell (fig. 3) and/or require a number of assembly components (fig. 4).

According to the invention, the traditional insulation system of the inner shell obtained by means of an air gap is replaced by a more efficient system. According to the invention, the inner casing 100 is made up of a plurality of annular members 400, which annular members 400 are arranged axially adjacent along the longitudinal axis 24 of the member (coinciding with the longitudinal axis of the turbine engine). The annular member 400 may be an annular collar 50 (as shown in fig. 5) or may be a circumferential combination of two or more collars 50 having angular segments. For example, in fig. 6, two ferrules having 180 ° angular segments are assembled in their circumferential direction to form an annular ferrule.

Each ferrule is a component, preferably unitary, having a region-wise porosity. Accordingly, the collar 50 includes a body 51, the surface of the body 51 being entirely covered by a layer forming a heat insulating sleeve 52, the heat insulating sleeve 52 having a porous structure, the function of which is to insulate the body 51. Thus, the sleeve 52 forms a porous interface around the body 51 that is thermally insulated from the external environment.

As shown in fig. 5 and 6, showing a cross-sectional view transverse to the longitudinal central axis 24 of the ferrule, the sleeve 52 includes an outer cover portion 52a that completely covers the radially outer surface of the body 51, and an inner cover portion 52b that completely covers the radially inner surface of the body 51. The lateral cover portions (not visible in this cross-sectional view) completely cover the longitudinal both ends of the main body 51 and connect the inner and outer portions.

The collar 50 also includes a protective sleeve 53 that at least partially covers the insulating sleeve.

As shown in fig. 5 and 6, the protective sheath 53 includes a radially outer protective portion 53a covering the outer covering portion 52a, and a radially inner protective portion 53b covering the inner covering portion 52b. The protective sleeve can be a coating deposited on the sleeve.

When the ferrule is a ferrule having angular segments, as shown in fig. 6, the ferrule includes two opposing circumferential ends 49; the insulating sleeve 52 further includes an intermediate cover portion 52c which completely covers the two circumferential ends 49 of the main body 51 and connects the outer cover portion 52a and the inner cover portion 52b. As shown in fig. 6, the cover 53 includes an intermediate protection portion 53c that connects the radially outer protection portion 53a and the inner protection portion 53b and completely covers the intermediate cover portion 52c of the insulating sleeve 52.

The protective sheath 53 is preferably dense with a volume porosity of at most 5% (excluding the limits).

Preferably, the sleeve 52 is located near the interface with the air and thus near the skin of the ferrule.

The sleeve 52 must have a good compromise between volumetric porosity, mechanical resistance and coefficient of expansion. The inventors have observed that lattice structures and microporous structures can provide all of these functions.

Thus, the sleeve 52 may have a lattice structure, i.e., a rigid structure composed of an open skeletal or frame, formed of connecting members, such as rods, beams, or similar types of connecting members, which may be straight or curved and contact, intersect, or overlap in a repeating pattern in three dimensions. The repeating pattern may be, for example, cubes, hexagons, pyramids, spheres, etc., and the lattice will then be formed of interconnected cubes, interconnected hexagons, interconnected pyramids, interconnected spheres, etc.

Fig. 8a and 8b show examples of possible lattice structures: with a cube pattern (fig. 8 a) and with a hexagonal pattern (fig. 8 b).

The sleeve 52 may also have a microporous structure, wherein the repeating pattern may have a polygonal shape, such as triangular, square, rectangular, hexagonal, etc. Fig. 9 shows an example of a honeycomb structure having hexagonal cells. The cells form cavities 55 and the walls 54 of the cells form a solid material of porous structure.

In thermodynamics, the body 51 functions to provide thermal inertia to the skin of the inner shell, making it more reactive as the thermal conditions in the duct change. In mechanics, it acts to ensure the rigidity of all the skins of the inner shell under pressure (in particular pipes) and thermodynamic forces, ensuring low displacements.

In thermodynamics, the function of the insulating sleeve 52 is to thermally insulate the main body 51 from the outer surface of the inner shell. Thus, the porosity thereof is smaller than that of the body. Preferably, the body has a dense structure, i.e. with little or no porosity, preferably with less than 5% by volume porosity.

In mechanics, the sleeve 52 functions to integrate the various elements of the ferrule, namely the interior (body 51) and the exterior (i.e., the skin that may be formed by the protective sheath 53). It must therefore adhere to certain stiffness constraints (excessive deformation would be detrimental to the gap). Thus, the type and porosity range of the sleeve 52 is selected to be a compromise between thermal and mechanical properties.

The sleeve 52 is at least partially physically separated from the outer surface (i.e., skin) of the inner casing by a protective sleeve 53, at least over the portion of the sleeve that will be in contact with the fluid flow of the turbine engine. Thus, the protective sleeve 53 acts as a physical barrier between the sleeve 52 and the outer surface of the ferrule; preferably, the protective sheath 53 has little or no porosity (preferably less than 5% by volume porosity). In fact, the porous surface is rough, which is detrimental to aerodynamics (and yield), in particular in terms of the interface with the pipes, and also to the loss of load in the housing cavity, in the case of compressors, air is often used to sample the engine and the rest of the aircraft (cooling of the turbine, pressurization of the aircraft cabin, etc.).

A portion of the protective sheath 53 may be directed toward the upper blade platform by an abradable surface.

The body 51, the sleeve 52 (which covers the surface of the body entirely) and the protective sleeve 53 (which covers the sleeve partially or entirely) can be made in one piece, to obtain a single piece and a unitary part, with the advantage of avoiding an assembly step. This may be achieved by using additive manufacturing techniques. This makes it possible to replace the complex solution of insulating the inner shell skin by an air gap with a simple, more efficient, simpler to install, less number of parts needed, possibly smaller in size.

Additive manufacturing techniques enable one to manufacture three-dimensional parts with complex geometries from wear-resistant materials while also creating void areas that are optimized for optimal mechanical properties. Manufacturing techniques are well known and will not be described in detail. It mainly includes stereolithography, selective laser sintering, fuse deposition, laser melting and other methods.

Selective laser sintering is the sintering of small particles of plastic, metal or ceramic with a high power laser until a three-dimensional part to be formed is obtained. Within the scope of the present invention, metallic materials (metals or alloys) or ceramic materials will be used.

Fuse deposition utilizes a temporary transition from a solid material to a liquid state, typically by heating; extrusion nozzles are typically used to apply the material to the desired location.

The different regions of the ferrule 50 according to the present invention may be made of any material compatible with additive manufacturing that is capable of providing sufficient rigidity in the relevant regions and compatible with the intended use of the ferrule (particularly in terms of mechanical resistance and heat). Thus, these different regions of the ferrule (body, sleeve and protective sleeve) may be made of metallic and/or ceramic materials. For example, stainless steel, nickel alloy, titanium alloy, or the like may be used. These regions may be made of different or the same materials.

Two examples of an inner shell whose skin is insulated according to the invention are shown in fig. 10a and 11 a. As shown in fig. 10b and 11b (exploded views of fig. 10a and 11 a), the annular parts (annular collar 50 or collar 50 with angular segments) are connected to each other by seals 37 or are equipped with flanges and connected to each other by bolts 42. The ferrule may be formed from a single piece (an annular ferrule, as shown in fig. 6) or assembled from a plurality of ferrules with circumferential connection angle segments (fig. 7).

In fig. 10a and 10b, a circular strip of abradable material 46 is added to the collar 50 in line with the rotor blades 6. The strip 46 may be added to the ferrule or integrated into the ferrule by being manufactured directly in the protective sheath 53.

In fig. 11a and 11b, a sealing tab 48 is added to the protective sleeve 53 over the entire inner surface of the collar 50 to ensure sealing.

According to an alternative, indicated by reference numeral 56, shown in figures 10a and 10b, the protective sleeve 53 may partially cover the insulating sleeve 52. This is possible when the uncovered surface of the sleeve 52 is intended to be covered with another component, here by the hooks 44 acting as an accessory to the stator vanes 13, which enables the sleeve 52 to perform the insulating function of the body 51.

Reference documents

[1]EP 1 059 420。

Claims

1. An inner casing (100) collar (50) for a turbine engine, the collar being centered about a longitudinal central axis (24), characterized in that the inner casing collar is a unitary component having different regions, wherein:

-a first region forming a body (51) centred on the longitudinal central axis, the body comprising two longitudinal ends and being delimited by a radially inner surface and a radially outer surface with respect to the longitudinal central axis;

-the second region forms a sleeve (52) comprising:

a lateral covering portion entirely covering a longitudinal end of the main body;

an outer covering portion (52 a) completely covering the radially outer surface of the body along a section transverse to the longitudinal central axis (24);

an inner covering portion (52 b) entirely covering a radially inner surface of the body along a section transverse to the longitudinal central axis (24);

a lateral cover portion connecting the inner cover portion and the outer cover portion; and

-a third region forms a protective sleeve (53) at least partially covering the insulating sleeve (52) and comprising, along a section transversal to the longitudinal central axis (24):

-a radially outer protection portion (53 a) at least partially covering said outer covering portion (52 a); and

a radially inner protection portion (53 b) at least partially covering the inner covering portion (52 b);

and the heat insulation sleeve has a porous structure, and the volume porosity of the heat insulation sleeve is greater than or equal to 50%.

2. Ferrule according to claim 1, wherein the body (51) and the outer (52 a) and inner (52 b) cover portions each extend over 360 ° around the longitudinal central axis (24).

3. The ferrule of claim 1 wherein the body and both the outer (52 a) and inner (52 b) cover portions extend over the same angular sector of less than 360 ° about the longitudinal central axis (24).

4. A ferrule according to claim 3, wherein the main body (51) has two opposite circumferential ends (49) and the sleeve (52) further comprises an intermediate cover portion (52 c) connecting the outer cover portion (52 a) and the inner cover portion (52 b) and completely covering each opposite circumferential end of the main body.

5. The ferrule according to claim 4, wherein the protective sleeve (53) further comprises an intermediate protection portion (53 c) connecting the radially outer protection portion (53 a) and the inner protection portion (53 b) and completely covering the intermediate covering portion (52 c).

6. Ferrule according to claim 1, wherein the radially outer (53 a) and inner (53 b) protective portions of the protective sleeve completely cover the outer (52 a) and inner (52 b) cover portions of the sleeve, respectively.

7. The ferrule of claim 1, wherein the protective sleeve has a volumetric porosity of less than 5%.

8. The ferrule of claim 1 wherein the insulating sleeve (52) has a microporous structure.

9. The ferrule of claim 1 wherein the insulating sleeve (52) has a honeycomb microporous structure or lattice structure.

10. Ferrule according to claim 1, wherein the body (51), sleeve (52) and sleeve (53) are made in one piece by additive manufacturing to form a unitary component.

11. The ferrule according to any one of claims 1 to 10, wherein the ferrule comprises a strip of abradable material (46) integrated into the ferrule by being manufactured directly in the protective sheath (53).

12. Turbine engine inner casing (100) comprising at least two ferrules according to any of claims 1 to 11, said ferrules being arranged axially adjacent to each other.

13. A turbine engine equipped with the inner casing according to claim 12.

14. The turbine engine of claim 13, comprising rotor blades (6), and wherein at least one ferrule comprises a strip of abradable material (46) added to the at least one ferrule in line with the rotor blades (6).